/**
 * @author ：wang-ting
 * @Date：2025/3/21 23:45
 */
import java.util.Scanner;
public class Grade {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int grade = sc.nextInt();
        if(90 <= grade && grade <= 100){
            System.out.println("Grade is A");
        }else if(80 <= grade && grade <= 89){
            System.out.println("Grade is B");
        }else if(70 <= grade && grade <= 79){
            System.out.println("Grade is C");
        }else if(60 <= grade && grade <= 69){
            System.out.println("Grade is D");
        }else if(grade < 60){
            System.out.println("Grade is F");
        }else{
            System.out.println("Grade is error");
        }
    }
}
